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Always bogs down going uphill on long grade

My pickup always bogs down going up a grade, seems like its flooding out and it starts running real rough and vibrating bad, I have to let off gas and pull over .

Been to shop several times, no one seems to know what’s causing it.

“Seems like it’s flooding out…” Why do you say that?

Sounds more like fuel starvation. Does it matter whether the gas tank is full or near empty? Maybe a problem with the fuel pump or the fuel pickup in the gas tank being blocked or floating loose so that when gas sloshes back it won’t suck fuel properly.

What year is your Chevy?

Tester

Age, miles, service repair history, check engine light on? Info like that can help get to the problem. When was the fuel filter replaced? I had an older Jeep that ran fine on flat or mild grades, but bucked on steep hills, turned out to be the coil (only had a single coil) it was weak and started to fail under load. Once it was replaced it ran fine.

‘‘always’’ ?
Is this a new problem or has it occured since the truck was new ?

Up here an my altitude ( 6500 ) you’ll get that sort of thing as a constant

Answering all of the above could help. Two key reasons for loss of power under load are clogged catalytic converters and failing fuel pumps. Starting there would be a no brainer for most shops - so it would also help to say what has been checked when it’s been in the shop.

Good comments above. I’ll add, is it pinging when this happens? If so, double check the spark plug condition and gap.

If it is “flooding out” you should smell gas. Can’t make a guess without year,make, model, mileage and engine.

no gas smell, 1998 PU 1500,276,000, V-8

Maybe clogged fuel filter.

My father in law had a problem with losing power going uphill and it didn’t have to be a long hill.

The substrate in his catalytic converter had broken and was lying loose in the converter and when he went uphill it blocked the outlet.

I don’t know if you have this type of converter but go underneath and hit the converter with a rubber mallet or the side of your fist and see if it rattles inside.

My vote is clogged fuel filter.